How to... deadhead flowers
It’s a term you encounter often when reading about plants: “deadhead regularly to encourage more flowering.”
But if you’re new to gardening, this simple sentence can be less illuminating and more confusing.
What exactly is deadheading?
How do you do it?
On which plants?
And, most importantly, why?!
Why deadhead plants
The short answer to this question is the one you’ll read all the time: so that the plant produces more flowers. But to properly understand why the plant produces more flowers, it helps to understand a bit more about the ins and outs of how a plant functions.
For all their beauty, scent and appeal to humans, the botanical purpose of a flower on a plant is to attract pollinators to the plant, in order to spread pollen between plants so that the plant can create seeds and reproduce.
So, for example, a bee that lands on multiple sweet pea flowers will spread pollen between the plants. The pollen on one flower germinates and joins together with the flower’s ovule (basically, the egg in plant form) and they fuse, grow and create a seed (the plant’s version of a baby). The whole point of the plant, of the flower, is to create the seed, so once this has happened it will stop putting its energy into flowering (the flower has already played its part) and put its energy instead into growing the seed. Great for the plant, it’s got babies on the way and it’s going to create new plants, less good for the humans who want to grow some beautiful flowers.
And so, what’s the relevance of this quick overview of plant reproduction when it comes to deadheading? Well, when you deadhead a plant, you are removing the spent flower head, but also — crucially — the developing seed. Because you’ve just stopped the poor old plant meeting its purpose (to create seeds to reproduce) it puts more energy into creating more flowers, in order to attract more pollinators, and to have another go at producing seeds.
When to deadhead
If you are a growing a plant for cutting flowers to bring inside for a vase, for example zinnias or dahlias, you would generally be removing all of the flowers as they appear. In that case, you would only need to deadhead the odd flower you have missed, which goes over and starts to produce seed.
If you’re growing flowers to enjoy them in the garden on the plant, then deadhead as soon as the flower goes over and before it starts to set seed.
How to deadhead
In order to keep plants producing more flowers, you need to ensure that you remove the entirety of the old flower and the seed that is starting to grow within it. The exact location of the developing seed is different on different plants, but ,on the whole cutting below the flower will remove it. However, you also don’t want to leave a long stretch of bare stem, so it usually looks best (and reduces the risk of any diseases being able to enter the plant) if you cut back to the nearest leaf node.
The tools you need will vary according to the plant. Soft stemmed annuals grown as cutting flowers could be pinched back using only your fingernails or a pair of floral scissors. Thicker stemmed herbaceous plants will need a sharp pair of secateurs. A good rule of thumb when choosing the right tool for the job is to make sure you use one sharp enough to make the cut neatly in one go. Hacking repeatedly at a stem can cause damage to the plant and make it less likely to heal cleanly.
Which plants to deadhead
Not all plants will produce more flowers when deadheaded, so it’s always best to check before removing flowers, but it rarely harms a plant to cut off an old spent bloom.
However, if you’re growing a plant that has attractive seedheads, or berries or hips that you want to enjoy in the Autumn, then make sure not to deadhead these. And of course, if you want to collect seeds from a plant, then don’t deadhead them or they won’t be able to produce the seed.
A quick list of plants that especially benefit from deadheading includes: peonies, astrantia, roses (unless you are growing a variety for its rose hips, in which case make sure to leave some flowers on the plant), cosmos, hydrangeas, dahlias, zinnias and sweet peas. This is a far from exhaustive list, though, so if you’re unsure about any plant, a quick Google can usually give you the answer. Or take a look through our plant guides for more detailed growing information on some of our favourite plants.
